Phase field model of the nanoscale evolution during the explosive crystallization phenomenon

Abstract

Explosive crystallization is a well known phenomenon occurring due to the thermodynamic instability of strongly under-cooled liquids, which is particularly relevant in pulsed laser annealing processes of amorphous semiconductor materials due to the globally exothermic amorphous-toliquid-to-crystal transition pathway. In spite of the assessed understanding of this phenomenon, quantitative predictions of the material kinetics promoted by explosive crystallization are hardly achieved due to the lack of a consistent model able to simulate the concurrent kinetics of the amorphous-liquid and liquid-crystal interfaces. Here, we propose a multi-well phase-field model specifically suited for the simulation of explosive crystallization induced by pulsed laser irradiation in the nanosecond time scale. The numerical implementation of the model is robust despite the discontinuous jumps of the interface speed induced by the phenomenon. The predictive potential of the simulations is demonstrated by means of comparisons of the modelling predictions with experimental data in terms of in situ reflectivity measurements and ex-situ micro-structural and chemical characterization.

Recent Progresses and Perspectives of UV Laser Annealing Technologies for Advanced CMOS Devices

“…When melting the doped Si substrate, although the diffusivity of the dopants strongly enhances (typically towards the order of 10 −4 cm 2 s −1 , as reported in Ref. [27]), their diffusion is limited within the melted region, having a box-like profile [28][29][30][31].…”

“…In this article, when discussing LPER, we have a regime so-called "Secondary Melting (SM)" in mind rather than the one so-called "Explosive Melting (EM)". In SM, the melted (i.e., liquid) layer forms at the surface of the semiconductor substrate and simply extends downward [31,44]. On the other hand, in EM, a thin liquid layer (typically a few to 10 nm of thickness [45]) formed at the surface travels in the depth direction, inducing recrystallization into a polycrystalline state [31,44].…”

Simulations of the Ultra-Fast Kinetics in Ni-Si-C Ternary Systems under Laser Irradiation

“…The evolution model for the Ni-Si-C system is formulated in the framework of the phase-field model for the phase transition with temperature change driven by irradiation in the thermalization approximation. The reference model (e.g., [ 12 ] and the references therein) is based on self-consistent solutions of (a) the time-harmonic Maxwell equation for the calculation of the local heat source where the incident wave is characterized by the wavenumber , the laser fluence and the time dependence of the power pulse, (b) the Fourier law for the simulation of the temperature field evolution and (c) the phase-field equation simulating the evolution of the solid-liquid front in the case of a melting process. The model is mathematically formulated in terms of coupled non-linear partial differential equations (PDE), which can be solved numerically with a Finite Element Method (FEM) in a proper simulation mesh [ 13 ].…”

“…We use the following values of the phase-field parameters and while is a phase-field function determined according to the Karma-Rappel prescription: i.e., imposing that the diffuse interface model reproduces the sharp interface limit and the latent heat balance at the moving interface correctly [ 12 ]. We note that the factors of the non-linear phase-dependent term in Equations (2) and (3) are related to the particular phase field formulation applied (see [ 12 ] and the references therein for the derivation) with a phase function that recovers the liquid (solid) properties at the ( ) value. The speed law, as a function of the under/over cooling, is implemented in the expression is Fulcher-Vogel type [ 15 ]: …”

Study of recrystallization and activation processes in thin and highly doped silicon-on-insulator layers by nanosecond laser thermal annealing

“…The fast solidification of this new undercooled liquid and the corresponding release of latent heat allows the crystallization process to propagate rapidly through the entire amorphized layer. Hence the regrowth of the a-Si takes place by a combination of upward and downward explosive crystallization, giving rise to a polycrystalline material in the entire volume of the amorphized film [28,29]. However, for a laser energy density of 1.1 J/cm 2 (Fig.…”